Problem: 2 markers cost $2.38. Which equation would help determine the cost of 15 markers?
Explanation: There are several equations that could help determine the cost, each with a slightly different approach. We know the cost of 2 markers. We want to know the cost of 15 markers. We can write the numbers of markers as a proportion: $\dfrac{2}{15}$ We know 2 markers costs $2.38. We can let $x$ represent the unknown cost of 15 markers. The proportion of these costs can be expressed as: $\dfrac{\$2.38}{x}$ The cost changes along with the number of markers purchased, and so the two proportions are equivalent. $\dfrac{2}{15} = \dfrac{\$2.38}{x}$